Organic polymer materials are increasingly being used in the microelectronics and optoelectronics industries for a variety of applications. For example, the uses for such organic polymer materials include interlevel dielectrics, redistribution layers, stress buffer layers, leveling or planarization layers, alpha-particle barriers, and passivation layers for microelectronic and optoelectronic devices. Where such organic polymer materials are photosensitive, thus self-imageable, and therefore, offer additional advantage of reducing the number of processing steps required for the use of such layers and structures made therefrom. Additionally, such organic polymer materials enable the direct adhesive bonding of devices and device components to form various structures. Such devices include microelectromechanical systems (MEMS) and microoptoelectromechanical systems (MOEMS).
While polyimide (PI), polybenzoxazole (PBO) and benzocyclobutane (BCB) compositions have been materials of choice for many of the aforementioned applications due to their generally good thermal stability and mechanical strength, each of the above materials are either formed during curing from precursors that react to modify the polymer's backbone (PI and PBO) or to form such backbone (BCB) and thus generally require special handling conditions during curing to remove by-products that are formed during such curing and/or to exclude oxygen or water vapor that can prevent such curing. Additionally, the curing of such materials often requires process temperatures in excess of 250° C. (and as high as 400° C. for some materials), resulting in excessive and undesirable process costs. Therefore such materials can be problematic for some applications, e.g., redistribution and interlevel dielectric layers as well as direct adhesive bonding of a transparent cover over image sensing arrays.
Therefore it is believed that it would be advantageous to provide a material, useful for forming the aforementioned structures, that exhibits thermal stability and mechanical strength equivalent to the known PI, PBO, and BCB compositions, where such a material has a fully formed polymer backbone that allows for curing at temperatures of 200° C. or lower. Further, such an advantageous material should be tailorable in its characteristics to provide appropriate levels or values of stress, modulus, dielectric constant, elongation to break and permeability to water vapor for the application for which it is intended. Still further, it would be advantageous for such a material to be self-imageable. In addition, several of the presently available compositions may not be suitable in certain of the applications as they do not exhibit the required dissolution rate (DR) properties, including desirable resolution and photospeed, as further described in detail below.
Accordingly, there is still a need to develop self imageable photosensitive polymer compositions which feature desirable thermal properties, dissolution rate, orthogonality to various solvents used in different steps of the device fabrication processes, bond adhesion, and most importantly integration into all involved process steps.